利用諾基亞 UI API處理聲音標題

 Sound類封裝了用於播放聲音的方法，手機所能支撐的聲音格局和並行播放的數目是和設備相干的，我們可以通過方法supportedFormat = Sound.getSupportedFormats();
Sound.getConcurrentSoundCount()方法得到這些數據。下面供給一個小程序用戶判定我的手機nokia 6108所能支撐的聲音類型和並行播放的數目。

package com.J2MEdev.test;

import Javax.microedition.lcdui.Display;
import Javax.microedition.lcdui.Form;
import Javax.microedition.midlet.MIDlet;
import Javax.microedition.midlet.MIDletStateChangeException;
import com.nokia.mid.sound.* ;

public class 諾基亞Sound extends MIDlet
{

    private Display display;

    private Form mainForm;

    private int[] supportedFormat;

    protected void startApp() throws MIDletStateChangeException
    {

        initMIDlet();

    }

    public void initMIDlet()
    {
        display = Display.getDisplay(this);
        mainForm = new Form("諾基亞 Sound");
        supportedFormat = Sound.getSupportedFormats();
        if (supportedFormat.length == 0)
        {
            mainForm.append("No audio format supported!");
        } else
        {
            for (int i = 0; i < supportedFormat.length; i++)
            {
                mainForm.append("" + supportedFormat[i] + " : "
                        + Sound.getConcurrentSoundCount(supportedFormat[i]));
            }
        }
        display.setCurrent(mainForm);
    }

    protected void pauseApp()
    {

    }

    protected void destroyApp(boolean arg0) throws MIDletStateChangeException
    {

    }

}

程序運行在nokia 6108上顯示1:1表現本機支撐單音，並行播放數目也是1。

    Sound類有兩個結構器
Sound(byte[] data, int type) 
         Sound(int freq, long duration)
我們重要講述後者，通過供給應結構器或者init(int freq,long duration)方法適當的頻率和持續時間來初始化聲音對象，通過調用play()方法可以播放聲音，調用stop方法可以停止聲音的播放。關於Sound類供給的其他API請參考諾基亞 Ui Java doc。這裡給出頻率參數
Freq off               0
 Ring freq A0           220
 Ring freq B0b          233
 Ring freq B0           247
 Ring freq C0           262
 Ring freq D0b          277
 Ring freq D0           294
 Ring freq E0b          311
 Ring freq E0           330
 Ring freq F0           349
 Ring freq G0b          370
 Ring freq G0           392
 Ring freq A1b          416
 Ring freq A1           440
 Ring freq B1b          466
 Ring freq B1           494
 Ring freq C1           523
 Ring freq D1b          554
 Ring freq D1           587
 Ring freq E1b          622
 Ring freq E1           659
 Ring freq F1           698
 Ring freq G1b          740
 Ring freq G1           784
 Ring freq A2b          831
 Ring freq A2           880
 Ring freq B2b          932
 Ring freq B2           988
 Ring freq C2           1047
 Ring freq D2b          1109
 Ring freq D2           1175
 Ring freq E2b          1245

Ring freq E2           1319
 Ring freq F2           1397
 Ring freq G2b          1480
 Ring freq G2           1568
 Ring freq A3b          1661
 Ring freq A3           1760
 Ring freq B3b          1865
 Ring freq B3           1976
 Ring freq C3           2093
 Ring freq D3b          2217
 Ring freq D3           2349
 Ring freq E3b          2489
 Ring freq E3           2637
 Ring freq F3           2794
 Ring freq G3b          2960
 Ring freq G3           3136
 Ring freq A4b          3322
 Ring freq A4           3520
 Ring freq B4b          3729
 Ring freq B4           3951
 Ring freq C4           4186
 Ring freq D4b          4434
 Ring freq D4           4698
 Ring freq E4b          4978
 Ring freq E4           5274
 Ring freq F4           5588
 Ring freq G4b          5920
 Ring freq G4           6272
 Ring freq A5b          6644
 Ring freq A5           7040
 Ring freq B5b          7458
 Ring freq B5           7902
 Ring freq C5           8372
 Ring freq D5b          8870
 Ring freq D5           9396
 Ring freq E5b          9956

 Ring freq E5           10548
 Ring freq F5           11176
 Ring freq G5b          11840
 Ring freq G5           12544
 Ring freq A6b          13288

    下面我們編寫一個小程序來講述如何應用諾基亞 UI來處理聲音標題，我們的目標是當用戶按下按鍵的時候開端播放聲音，當用戶開釋按鍵的時候結束播放，我們供給一個ToneCanvas類來顯示用戶按下的鍵，並通過TonePlayer類來播放適當頻率的聲音。

package com.J2MEdev.tone;

import Javax.microedition.lcdui.Canvas;
import Javax.microedition.lcdui.Graphics;

import com.nokia.mid.ui.FullCanvas;

public class TonesCanvas extends FullCanvas
{

    private TonesMIDlet midlet;

    private int pressNum;

    private int currentKey;

    private TonePlayer player = new TonePlayer();

    private static int freq[][] = { { 523, 554 }, { 587, 622 }, { 659, 659 },
            { 698, 740 }, { 784, 831 }, { 880, 932 }, { 988, 988 },
            { 1047, 1109 }, { 1175, 1245 }, { 1319, 1319 }, { 1397, 1480 } };

    public static final int NAT = 0;

    public static final int SHARP = 1;

    private int x = this.getWidth() / 2;

    private int y = this.getHeight() / 2;

    private boolean sharp = false;

    public TonesCanvas(TonesMIDlet midlet)
    {
        super();
        this.midlet = midlet;
        // TODO Auto-generated constructor stub
    }

    public void paint(Graphics g)
    {
        if (pressNum == -1)
        {
            return;
        }
        String note = (sharp == true) ? "#" : "";
        g.setColor (128, 255, 18);
        g.fillRect(0, 0, getWidth(), getHeight());
        g.setColor(124, 124, 0);

        g.drawString(pressNum + note, x, y, Graphics.LEFT | Graphics.TOP);

    }

   public void keyPressed(int keyCode)
    {
        if (keyCode == Canvas.KEY_POUND)
        {
            sharp = !sharp;

        } else
        {
            switch (keyCode)
            {
            case Canvas.KEY_NUM0:
                pressNum = 0;
                break;

            case Canvas.KEY_NUM1:
                pressNum = 1;
                break;

            case Canvas.KEY_NUM2:
                pressNum = 2;
                break;

            case Canvas.KEY_NUM3:
                pressNum = 3;
                break;

            case Canvas.KEY_NUM4:
                pressNum = 4;
                break;

            case Canvas.KEY_NUM5:
                pressNum = 5;
                break;

            case Canvas.KEY_NUM6:
                pressNum = 6;
                break;

            case Canvas.KEY_NUM7:
                pressNum = 7;
                break;

            case Canvas.KEY_NUM8:

pressNum = 8;
                break;
            case Canvas.KEY_NUM9:
                pressNum = 9;
                break;
            case Canvas.KEY_STAR:
                pressNum = 10;
                break;

            default:
                pressNum = -1;
                break;
            }
            if (pressNum != -1)
            {
                player.play(freq[pressNum][sharp == false ? NAT : SHARP]);

            }
        }

        currentKey = keyCode;
        repaint();

    }

    public void keyReleased(int keyCode)
    {
        if (keyCode == currentKey)
        {
            pressNum = -1;
            player.stop();
        }
        repaint();

    }

}
package com.J2MEdev.tone;

import com.nokia.mid.sound.Sound;

public class TonePlayer
{

    private Sound sound;

    public TonePlayer()
    {
        super();
        sound = new Sound(0, 2000);

    }

    public void play(int freq)
    {
        sound.init(freq, 2000);
        sound.play(1);
    }

    public void stop()
    {
        sound.stop();

}

}

package com.J2MEdev.tone;

import Javax.microedition.midlet.*;
import Javax.microedition.lcdui.*;

public class TonesMIDlet extends MIDlet
{
    private final TonesCanvas canvas;

    public TonesMIDlet()
    {
        canvas = new TonesCanvas(this);
    }

    public void startApp()
    {
        Display.getDisplay(this).setCurrent(canvas);
    }

    public void pauseApp()
    {
    }

    public void destroyApp(boolean unconditional)
    {
       
    }

    void exitRequested()
    {
        destroyApp(false);
        notifyDestroyed();
    }
}